This is a proposal for five years of support, to complete Biomedical Engineering PhD training at the University of Michigan (UM) in the biomechanics of trunk control in older adults, a major issue in avoiding falls. The career development plan includes coursework to develop competencies in biomechanical modeling and neuromuscular control participation in joint seminars at the mentor's laboratories, participation in seminars related to aging at the UM Institute of Gerontology, presentation at national meetings, and submission of manuscripts for publication. A research project has been identified that will eventually lead to a more specific thesis. Three aims are proposed for the research plan: 1) Identify biomechanical factors governing trunk control in healthy and fall-risk older adults, including trunk strength, velocity, and proprioception under static and dynamic conditions;2) Assess the relationship between these factors and clinical tests of fall risk;and 3) Model trunk control system dynamics, particularly under conditions of muscle function or sensory deficits. Primary mentor will be Nell Alexander MD, Director of the Mobility Research Center, who has extensive experience in aging mobility studies, particularly in postural control. Co-mentor will be James Ashton-Miller PhD, biomechanical engineer and Director of the Biomechanics Research Laboratory.